Stability measurements of microwave frequency synthesis with liquid helium cooled cryogenic sapphire oscillators

TL;DR

This paper evaluates the stability of microwave frequency synthesis using cryogenic sapphire oscillators, demonstrating high stability and precise frequency synthesis over a wide range of integration times.

Contribution

It presents a novel method of synthesizing arbitrary microwave frequencies with cryogenic sapphire oscillators combined with an H-maser, achieving unprecedented stability.

Findings

Fractional frequency stability below 4×10^{-15} for 1 to 10,000 seconds

Comparison shows synthesized signals match reference oscillator stability

Cryogenic sapphire oscillators enable highly stable microwave synthesis

Abstract

We report on the evaluation of microwave frequency synthesis using two cryogenic sapphire oscillators developed at the University of Western Australia. A down converter is used to make comparisons between microwave clocks at different frequencies, where the synthesized signal has a stability not significantly different from the reference oscillator. By combining the CSO with a H-maser, a reference source of arbitrary frequency at X-band can be synthesized with a fractional frequency stability of sub-$4 \times 10^{-15}$ for integration times between 1 s and 10,000 s.